Various generator principles are available for the conversion of mechanical energy into electrical energy. The functional components are designed differently depending on the generator size. In very large generators, coils are typically used for generating the magnetic field in order to avoid expensive permanent magnets. However, the generation of the magnetic field by means of an electric current is always associated with losses that deteriorate the efficiency. It is therefore common practice to use permanent magnets in small and medium-sized generators. The energy conversion is frequently realized with the inversion of the d.c. motor or synchronous motor principle and more rarely with the inversion of the asynchronous motor principle.
In addition, there also exist so-called transverse flux machines, but these machines are not widely used other than as automobile generators. The main problem of transverse flux machines is their structure, which is usually associated with unreasonably high manufacturing costs. This can be attributed, in particular, to the required complicated geometry of the flux-conducting components. Claw pole generators represent a special type of transverse flux machines. Claw pole generators have been used in large quantities as generators in the automotive industry for quite some time (see, for example, DE 10 2007 016 558 and DE 10 2004 032 684). Claw pole generators are furthermore described in documents DE 101 06 519 and DE 102 29 198, wherein a claw pole generator without slip ring is described in DE 39 17 343. Document DE 10 2012 001 114 discloses a design of a stator for a transverse flux machine.
A miniaturized claw pole generator is disclosed in document DE 102 17 285.
The main disadvantage of conventional claw pole machines is their high detent torque. This detent torque can in fact be slightly reduced with a suitable design of the claws. However, it could not be eliminated in any claw pole machines known so far due to the corresponding structural design.
The demand for miniaturized generators for the electrical supply of low consumer loads has significantly increased in recent years. These miniaturized generators serve for supplying devices with energy in an autarkic fashion in order to thereby make available new functions. These functions frequently concern the acquisition and wireless relaying of sensor data. The required power is frequently so low such that conversion principles other than electromagnetic generators, for example piezoelectric generators, are also explored. However, their power output is significantly lower such that they are only suitable for special applications. This field is generally referred to as “energy harvesting.” As the interlinking of sensors in the industrial environment and in all types of consumer electronics increases, the demand for miniaturized generators will also continue to increase in the future.